| 摘要 |
PURPOSE:To ensure the stable and accurate reading of the digital modulated signal, by comparing a modulated signal of a modulating system in which a high- level period is equal to a low-level period with a prescribed comparing level and then detecting the time moduli of high and low levels to control the prescribed comparing level. CONSTITUTION:An FM signal is recorded to a laser disk, etc. so that the mean time moduli are approximately equal to each other between a high level and a low level. A reproduced signal of such FM signal is used for a forward phase input of a comparator 2 via a capacitor C1, and a prescribed comparing level is applied to a backward phase input. These inputs are fed to a D-FF5 and an edge detector 3 to undergo a signal process. An LPF containing a resistance R7 and a C9 and an LPF containing an R8 and C10 as well as an inverter 6 are provided in order to detect the time moduli of high and low levels for the output of the comparator 2. The time moduli are fed to a differential amplifier 11, and the prescribed comparing level of the comparator 2 is controlled by a differential output. In such a way, a faithful reproduction is possible for the signal which passed through a recording or transmitting system in which a high level and a low level are asymmetrical to each other. |
